The present invention relates to applying solid carbon dioxide snow onto an object (such as a product to be chilled or frozen, or a belt of a refrigeration device for carrying out such chilling or freezing).
Typically, application of CO2 snow is accomplished through a device called a snow horn. Snow horns usually are loud, fairly large devices that typically need to be operated in a vertical orientation and typically are subject to plugging and non-uniform flow. The flow from typical snow horns can be difficult to distribute uniformly across a wide array of products or a wide belt.
Snow is applied onto a belt to prevent product from sticking to the belt and to provide refrigeration. The product to be chilled or frozen is typically dropped onto the belt downstream of the snow horn. The height of the snow horn usually determines how far the product drops before it comes in contact with the snow on the belt. As it is desirable to minimize the distance through which the product is dropped, it is desirable to minimize the size of the snow horn.
The prior art describes other attempts to form and agglomerate carbon dioxide snow using a snow horn.
U.S. Pat. No. 4,111,671 describes a method and apparatus for separating CO2 snow from a mixture of snow and vapor. The method consists of expanding liquid CO2 into a rectangular conduit of continuously increasing cross section to create a flow of solid and vapor CO2 in the conduit, conducting this flow around a curve, and separating the snow on the outer edge of the curve by a physical separation barrier. The apparatus for separating the snow consists of a rectangular conduit of continuously increasing cross section, means for introducing mixture of CO2 snow and vapor, conduit having a curved section to concentrate the solid CO2, and a blade for separating the concentrated solid from the vapor.
U.S. Pat. No. 4,444,023 discusses a horn design wherein liquid CO2 is expanded into a curved horn of increasing rectangular cross section. The horn has an opening to atmosphere on the inner curved surface. The solid CO2 travels along the outer portion of the curve and the pressure differential created by the opening to atmosphere causes the solid CO2 to be spread evenly along the outer curved surface. Ribbons of solid CO2 are discharged from the horn in a uniform pattern for application typically on a belt.
U.S. Pat. No. 4,652,287 discusses a rectangular horn/injector design for producing a uniform flow of solid CO2 over a rectangular area. The liquid CO2 is injected in the upper region of the horn and expanded in a funnel section. Baffles are provided in the upper section that separate the CO2 injectors and cause the resulting solid CO2 to fall generally downward and uniformly through out the cross sectional area of the horn.
U.S. Pat. No. 5,450,732 discusses an apparatus for distributing cryogen onto a belt. It is composed of a closed housing (either circular or rectangular in cross section) with a slot across the length of the housing for forming and distributing a curtain of cryogen onto a product to be frozen. Cryogen is injected into a manifold mounted in and axial to the housing. The cryogen is injected in all directions radially through a plurality of apertures in the manifold or a sintered metal tube.
U.S. Pat. No. 6,000,238 discusses a device for carbon dioxide snow blanketing. The device includes a housing with at least one passageway for delivering CO2. Where one end of the passageway is connected to a carbon dioxide generator and the other end is placed over the substrate onto which CO2 snow is to be deposited. A means for heating the passageways is provided to prevent the solid CO2 from adhering to the walls and plugging up the passageway is provided.
U.S. Pat. No. 6,023,941 discusses a carbon dioxide snow horn that operates either vertically or horizontally and can be adjusted to produce different consistency CO2 snow. The basic apparatus contains an inlet tube for receiving liquid CO2, an outlet tube for dispensing solid CO2, and a porous member located either within or at the end of the inlet tube for the expansion of the liquid CO2 into solid and vapor.
U.S. Pat. No. 6,151,913 discusses a method and apparatus for agglomeration of fine snow particles. The device includes an individual snow horn connected to an expansion device with multiple fine channels. The horn agglomerates the flow from the expansion device.
European patent application EP 0721801 discloses a jet spray nozzle configured and operated to propel particles of solid CO2 out of the nozzle onto a surface at sufficiently high velocity to dislodge even minute contaminants from the surface, thereby cleaning the surface. The difference between this disclosure and the present invention is comparable to the difference between a particle beam gun and a snowmaking machine.
One aspect of the present invention is a device useful for delivering carbon dioxide snow, comprising
a supply conduit for providing a flow of pressurized carbon dioxide, the conduit having an axis and a wall extending along and surrounding said axis;
a plurality of tubes disposed side by side, each tube having a constant cross-sectional configuration and area throughout its length, each tube having a first end the peripheral edges of which are sealed to the outside of the conduit wall and a second end which is open to the ambient atmosphere, wherein the axis of each tube at least at said first end is perpendicular to said conduit axis;
a plurality of apertures through the conduit wall, there being at least one aperture communicating with the interior of each of said plurality of tubes;
the apertures being dimensioned to enable pressurized carbon dioxide to flow therethrough from the conduit interior into a corresponding tube and to expand to solid carbon dioxide and carbon dioxide vapor; the tubes being dimensioned in length and width so that said solid carbon dioxide agglomerates in the tube into snow.
Another aspect of the present invention is a method of providing carbon dioxide snow, comprising supplying a pressurized flow of liquid carbon dioxide into the conduit of the aforementioned device, whereupon the carbon dioxide flows through said apertures and expands to form solid carbon dioxide and carbon dioxide vapor in said tubes, and said solid carbon dioxide agglomerates in said tubes into snow.
A further aspect of the invention comprises applying the carbon dioxide snow thus formed onto an article or surface.